Conventionally, in optical communications using an optical transmission member such as an optical fiber and an optical waveguide, an optical module including a light emitting element such as a surface-emitting laser (for example, VCSEL: Vertical Cavity Surface Emitting Laser) has been used. The optical module includes an optical receptacle which allows for incidence of light containing communication information emitted from a light emitting element on an end surface of the optical transmission member.
In addition, for the purpose of adjusting the light output or stabilizing the output characteristics of a light emitting element against temperature variation, some optical modules include a detection element for checking (monitoring) the intensity and the quantity of the light emitted from the light emitting element.
For example, PTL 1 discloses an optical module including a photoelectric conversion device in which a light emitting element and a detection element are disposed, and an optical receptacle configured to optically connect the light emitting element and an end surface of an optical transmission member.
The optical module disclosed in PTL 1 includes the photoelectric conversion device and the optical receptacle. The optical receptacle includes a first optical surface on which light emitted from a light emitting element is incident; a second optical surface configured to emit light advanced through the inside of the optical receptacle is condensed at an end surface of the optical transmission member; a reflection surface configured to reflect, toward the second optical surface, light which is incident on the first optical surface; a light separation part configured to separate light reflected by the reflection surface into monitor light travelling toward the receiving element and signal light travelling toward an end surface of the optical transmission member; and a third optical surface configured to emit the monitor light toward the detection element. In addition, the light separation part includes a division reflection surface that is an inclined surface inclined to the optical axis of light reflected by the reflection surface and is configured to reflect a part of light reflected by the reflection surface toward the detection element; a division transmission surface that is a surface perpendicular to the optical axis and is configured to allow the other part of the light reflected by the reflection surface to pass therethrough toward the second optical surface; and a division step surface that is a surface parallel to the optical axis.
In the optical module disclosed in PTL 1, the light which is emitted from the light emitting element and is incident on the first optical surface is reflected at the reflection surface toward the light separation part. The light reflected by the reflection surface is separated by the light separation part into signal light and monitor light. The monitor light separated by the light separation part is emitted from the third optical surface toward the light reception surface of the detection element. On the other hand, the signal light separated by the light separation part is emitted from the second optical surface toward an end surface of the optical transmission member. As described, PTL 1 discloses an optical module of the transmission side which includes an optical receptacle configured to couple light emitted from a light emitting element with an end surface of an optical transmission member.